Process of removing color from cotton seed oil and the like



Aug. 20, 1957 P. A. WILLIAMS PROCESS OF REMOVING COLOR FROM COTTON SEEDOIL. AND THE LIKE Filed Jan. 30, 1953 2 Sheets-Sheet l u tLwx J W m R.l-\ m N Wm A 5 mm mmqzfim 2 s w 2 9 A M. C r 9 e L7 a m N x 32m m 11 Q mw i v om wuiuq m @EEEMQ .5 a M m WM. hm gm .ot w A 1 v E 35 W S GQEXQTQQW wmbuitzud Aug. 20, 1957 P. A. WILLIAMS 2,803,635

PROCESS OF REMOVING COLOR FROM COTTON SEED OIL AND THE LIKE Filed Jan.30, 1953 2 Sheets-Sheet 2 Porfer A. Wf/Uams INVHVTOR.

ATTORNEY 2,803,636 Patented Aug. 20, 1957 PROCESS OF REMOVING COLOR FROMCOTTON SEED OIL AND THE LIKE Porter A. Williams, Houston, Tex.

Application January 30, 1953, Serial No. 334,172

6 Claims. (Cl. 260425) This invention relates to a process of removingcolor from vegetable oils such as cotton seed oil, peanut oil, linseedoil, soya bean oil, sesame oil, and the like.

It is an object of this invention to provide a process of removing colorfrom cotton seed oil, and the like, by re-refining methods whichcomprise the substantially instantaneous dispersion of a causticsolution into the oil whereby the color bodies of the oil may be soamply and intimately contacted by a minimum quantity of the causticrefining agent with a resultant maximum removal of color bodies at aminimum refining loss.

It is another object of this invention to provide a process whichmaintains the oil and caustic in a closed system whereby theirsubstantially instantaneous mixture is accomplished without theincorporation of excessive air.

It is still a further object of this invention to provide a processwhich utilizes caustic soda solutions in high concentrations above 40Baum and somewhere near the point of saturation for the governingtemperature and by minimizing tat saponification and improving theeffectiveness of color removal, such solutions being maintained attemperature above the critical minimum temperatures required to maintainthe caustic in solution.

It is yet another object of this invention to provide a process of thisclass which permits the oil to be re-refined at a wide range oftemperatures.

It is also another object of this invention to provide a process of thisclass which employs as a mixing device a machine having mechanical rotormeans rotatable at excessive speeds to agitate the oil and caustic to bemixed within the limited space or passageway.

It is yet a further object of this invention to provide a process ofthis class in which the mixture of oil and solution in passing by highspeed rotatable means passes through a passageway which is subject toadjustment of opening down to a point of grinding contact.

It is yet another object of this invention to provide a process of thisclass which may employ pressures to force the mixture through apassageway of the machine which pressures vary in accordance with thestructural limitations of the machine, the passageway opening and thethroughput.

It is still a further object of this invention to provide a process ofthis class in which the throughput of the machine is a function of thehead pressure and the width of the pasageway opening.

It is also a further object of this invention to provide a process ofthis class in which the mixture from the machine may be subsequentlytreated so as to utilize either separation by gravitation or by acontinuous process involving the use of centrifugal separation.

It is yet another object of this invention to provide a process of thisclass in which the mixture of oil and solution passes throughpassageways providing abrasive surfaces.

It is yet a further object of this invention to provide a process ofthis class in which the mixture of oil and solution passes throughpassageways, the component Wall forming parts of which comprise highlyrelatively rotatable means.

It is yet another object of this invention to provide a process of thisclass in which the oil is mixed with caustic soda solutions of such highconcentrations as to produce a lighter colored oil than heretoforeobtainable.

It is an object of this process through the substitution of a thoroughdispersion for conventional mixing to provide a continuous process whenused in conjunction with centrifuges wherein a simplification ofmachinery either by an increased capacity is achieved per unit machineor a simplification of machinery is achieved through substitution of oneunit for a multiplicity of mixing units.

It is an object of this invention to provide a batch process fordecolorizing oil wherein through the use of a most ettective dispersiontreatment it eliminates the effect of the contact time element therebyproviding a process of high capacity associated with a minimuminvestment and unit machinery requirement.

It is yet a further object of this invention to provide a process ofthis class in which the mixing step is accomplished in a matter ofseconds, a second or fractions of a second as compared with theconventional methods heretofore employed which require several minutesin the mixing step.

It is yet a further object of this invention to provide a process ofthis class which may optionally employ a blender prior to the high speedmixing step.

It is also another object of this invention to provide a process of thisclass in which the mixture of oil and caustic is so produced that thesubsequent time elapsing between the mixing step and the completion ofthe process has no further effect upon the loss sustained.

In processing some cotton seed oil and the like by conventional refiningmethods, regardless of the efliciency of the method, some oils will havea dark, refined oil color which cannot be readily bleached byconventional bleaching methods. Such oils have a limited use unless theyare subsequently subjected to another refining process to improve theirbleachability, and this subsequent process is termed the re-refining orlye-washing process.

In general, the lye-washing process comprises mixing the oil with apredetermined quantity of relatively weak lye. Then, after theexpiration of a certain agitating time, with or without the subsequentaddition of water, the agitation is discontinued. Then, the aqueousphase, containing neutralized acids and some fat and coloring matter, isallowed to settle and is subsequently drawn oil. This conventionallye-washing has been carried out by two types of processes; one being abatch process involving separation by gravitational settling; the otherbeing a continuous process involving the use of centrifugal separation.

The batch process of re-refining consists essentially of adding a smallquantity of caustic soda in concentration up to saturation, stirring themixture from one-half to three hours. After expiration of desired mixingtime and while the agitation is still continuing, water is added in suchquantity as to produce a soap which readily agglomerates when theagitation is slowed and settles when it is discontinued. Separation isgravitational and takes place in a relatively short time.

The second method of re-refining consists of mixing oil and relativelyweak lye in concentration usually lying between 14 and 24 Baum, whilethe oil and lye are traveling through a continuous mixer the period ofagitation is relatively short, usually in the neighborhood of fiveminutes. The oil and lye mixture is heated, either before or aftermixing, usually after mixing, and is then subjected to centrifugalseparation for purposes of removing the semi-solid soap stock from therefined oil.

In exploring the possibility of improvement of the batch process,Kavanagh, in his publication in The Journal of the American Oil ChemistsSociety, September 1951, made the following observations: The efiiciencyof color removal is directly proportional to the strength of causticsoda used, the length of time of high speed stirring, the amount ofcaustic soda used, and the speed of agitation, but inverselyproportional to the temperature of the oilcaustic soda mixture." Nocomparative loss figures were given; however, statements were made tothe effect that refining loss increased rapidly when the amount ofalkali added was increased, especially with high concentration of sodiumhydroxide solutions; refining loss increased only slightly at lowtemperature but increased rapidly at high temperature as the time ofagitation was prolonged. Relatively larger percentage of 20 Baum orweaker caustic soda solution can be used at temperatures below 85 F.without encountering undue enlarged refining losses and with higherconcentration of caustic soda solution it is essential to use theminimum percentage by weight of alkali in order to avoid undue highrefining losses."

Kroonen, in a publication in The Journal of the American Oil ChemistsSociety" of February 1952, and after the process of this invention wasdeveloped, on pursuing the type of re-refining proposed by Kavanagh,again showed that oils re-refined by a so-called high-sheer" methodshowed less residual color than conventionally re-refined oils; theircolor removal was most rapid during the first five minutes andpractically complete in ten minutes; the optimum concentration of lyefor color removal was between .1 and .2 percent sodium hydroxide; thatoptimum concentrations of sodium hydroxide was between 20 and 30 Baum;that color removal improved as the temperature dropped and that lossesencountered by this method of re-refining were almost identical to thoselosses encountered by conventional methods.

It can be seen that this invention departs in substance and theory fromboth Kavanagh and Kroonen as to its method steps and as to its obtainedresults. In such invention the refined oil is fed by gravity or pumpedunder superatmospheric pressure through a flow measuring device into aconduit. Caustic from above 40 to 60 Baum, preferably in the form of afully saturated solution in the neighborhood of 50 Baum, is likewise bymeans of gravity or under superatmospheric pressure fed through ametering device into the same conduit. This mixture then flows into amechanical mixing device; such as (but not limited to), a conventionalcone blender, rotating at about 900 R. P. M. This first mixing device isused to put the two immiscible solutions in condition so as to insurethe effectiveness of the following critical treatment, and is anoptional step.

The mixture is passed from the first preliminary blender into thedispersing device, one form of which consists of a set of stones; onefixed and one rotating. These stones are capable of adjustment withreference to the spacing between them. The mixture, in passing throughthe regulated spacing between the stationary and moving stones issubjected to an attrition which brings about a degree of dispersion;unobtainable by other means.

After being subjected to this dispersion treatment, the mixture may betreated either by a continuous or a batch process.

If treated continuously, the mixture is heated either before or afterthe admixture of sufficient water to bring the soap into a conditionsusceptible to centrifugal separation of oil from soap phase, acondition which is ordinarily carried out between 100 and 170 F.

If carried out on batch process, the mixture is allowed to accumulate tothe desired size batch and then is treated and admixed with water eitherbefore, after or during the heating. Sufiicient water is added so thatwhen the soap is agitated sulficient to keep it suspended within the oilphase it agglomerates to particles of such size and density as to makeit bring about a satisfactory separation through gravitation.

As shown in Fig. 1, the oil or liquid to be refined, is stored in tank 1from which the line 2, having the control valve 3 therein, extends forconnection to the suction side of the pump 4. This pump 4 dischargesinto the line 5, having the control 6 therein, and is supplied into themetering device 7 from which is flows, via the line 8, having thecontrol valve 9 and check valve 10 therein, to a blender 11.

The caustic tank 12 containing a saturated solution of NaOH, normallyabout 50%, at room temperature, has the line 14 therefrom, having thecontrol valve 15 therein, which is connected to the suction side of thepump 16. The pump 16 discharges through the line 17 having the strainer18 and control valve 19 therein, to the metering device 20. From themetering device 20, the caustic passes via the line 21 having thecontrol valve 22 and check valve 23 therein, into the line 8 to join theoil therein, and to flow with the oil to the blender 11.

The blender 11 forms a homogeneous admixture of the two immiscibleliquids and via the line 24, having the strainer 25 therein, it suppliesthe admixture to the junction of the line 26 and the line 27. if it isdesired to recirculate the admixture until such time as the proper oiland caustic balance is obtained, the valve 28 is closed and the valve 29is opened so that the admixture may flow back into the oil storagetank 1. The valve 30 is normally opened to admit the pressure of theliquid in the line to act on the gauge 31.

If it is desired to discharge the fluid directly to the fluiddispersator 32, the valve 29 is closed and the valve 28 is opened. Inthis machine the admixture is rotated at extremely high speeds, as 5400R. P. M., and passes by a paddle structure which acts as an agitator. Itthen passes through an angularly extending passageway between astationary stone and a rotatable stone revolving at say 5400 R. P. M.,such passageway being normally not greater than /2" in width.

The speed of the revolving stone may vary between 900 R. P. M. and15,000 R. P. M., depending upon desired throughput. Moreover, theoil-caustic mix may be added under a pressure varying from at leastatmospheric to approximately #/sq. in., again depending upon throughputand stone spacing. Conversely, the rate of throughput may vary between5000#/hr. and 42,000#/ hr,. or higher, depending upon pressure and stonespacing. The stone spacing may vary between almost actual contact andM1", or even greater. The construction of the dispersator, in detail,will be described hereinbelow.

The finely divided caustic is dispersed into the oil, where it reactswith the color bodies to facilitate their separation from the main bodyof the oil.

The discharge 33 is so constructed, that the air is easily and quicklyremoved from the dispersator. This is possible since the fluidcommunication area between the dispersator and the inverted U-shapedpipe 34 is great, so that air from the dispersator will rise upwardlytherein as the chamber fills with oil.

From the U-shaped pipe 34, having the valve 35 therein, the mixture maydischarge through the line 36 to conventional centrifugal machines, oroptionally it may discharge through line 37, having the valve 38therein, to the kettle 39 where the process of re-refining is completed.

The line 36 has the valve 48 therein between its junction with the line37 and the heat exchanger 50, which serves to cool the discharge fromthe dispersator 32. From the heat exchanger 50 the line 36 leads to thecentrifuge separator 51 which serves to separate the oil from the soapand saponified residues, the soap being discharged at 52 and the oil at53.

To supply water to the line 36, the line 54 is provided having the checkvalve 55 and valve 56 therein.

In case it may be desirable to wash out the caustic system, the valves44 and 45 in the line 46 are opened, the line 46 also having the checkvalve 47 therein adjacent the valve 44. Also the valve 42 in the line 41is closed, such line also having the check valve 43 therein. Also thebleeder valve 40 in the line 49 is closed, as is the valve in the line14. Then compressed air is injected into the line 46 to blow out thesystem. After this the valve 44 is closed and the valve 42 is opened toadmit water to wash out the system.

The details of the dispersator are shown in Fig. 2, disclosing one formof machine for carrying out the step of throwing a small quantity ofconcentrated caustic into intimate fixing contact with the color bodies.The principles on which machines of this type work consist of bringingthe oil and caustic mixture into contact with a rapidly revolving meansoperable in a limited space to complete the complete intermingling ofthe caustic and oil, and thereafter passing the intermingled oil andcaustic through an orifice of very restricted character between tworelatively rotatable elements, preferably abrasive stones.

The relative rotation may be obtained by rapidly revolving one element,or stone, with relation to a fixed element or stone, when there is avery limited passage or orifice between such elements. Optionally bothelements may be rotatable in the same direction but with a wide degreeof relative rotation being obtainable between the high speed and lowspeed elements. Also, the desired great relative rotation may beobtained by revolving one element, or stone, in one direction, and theother element, or stone, in the other direction.

In detail the dispersator 32, shown in Fig. 2, comprises the housing 60,which, as shown, may be mounted vertically, although this inventionconsiders machines which may be mounted with axis to extendhorizontally, as well. The intermingled oil and caustic enters the inlet61 from the line 27, and is brought into contact with the rapidlyrevolving impellers or paddles 62 in the mixing chamber 63. If, at thispoint the oil and caustic have not yet been thoroughly intermixed andintermingled, such is accomplished to completion in this chamber.

The housing 60 is mounted on the motor 64 which has its shaft 65coupled, by the coupling 66, to the shaft 70. Surrounding the couplingis an externally toothed ring gear 67, which is integrally connected tothe sleeve 68, which is threaded at 69 into the housing 60. The sleeve68 has the internal shoulder 71, which underextends the externalshoulder 72 of the shaft 70 and the lower ball bearing assembly 73.

The shaft 70 has the splines 74 thereon which fit into grooves 75 in theinner or wear sleeve 76, which wear sleeve extends between the lowerball bearing assembly 73 and the upper ball bearing assembly 77. Thebacking member 78 rests downwardly on the inner race of the lower ballbearing assembly 73 and the spacer member 79, and the sleeve 68 has theupper extension 80 which confines the spacer member 79 and outer race ofthe upper ball bearing assembly 77 in position.

The pinion shaft 81 is supported in the housing 60 outwardly of the gear67, and the pinion 82 thereon meshes with the gear 67. Thus, by turningthe pinion shaft handle 83 in the proper direction the pinion 82 causesthe gear 67 to rotate, and since the sleeve 68 is integrally connectedto the gear 67, and is threaded at 69 into the housing 60, the sleeve 68moves upwardly in the housing, and with it the sleeve shoulder 71 liftsthe shaft 70 and the lower ball bearing assembly 73, and the wear sleeve76, and the elements supported thereabove.

At the same time the pinion 82 maintains engagement with the gear 67 byvirtue of the width of the face of such gear, and the shaft 70 maintainsconnection with the motor drive by virtue of its lower end being splinedat 83 to fit in grooves in the coupling 66.

The backing member 78 supports, and has connected thereto, a discelement 84, which, in certain original usages of this type of machine,served as a grinding element, and such element was naturally of anabrasive substance, as Carborundum or stone. In the present usage suchelement 84 is shown to be of an abrasive substance, but the materialthereof is not necessarily a limitation, and other substances may beemployed and formed to the configuration to be hereinbelow described.

Such configuration comprises a flat base to rest upon the backingelement 78, a tapered portion, and a flat top. The insert 87 is pressedinto the disc element 84, and has the flange 88 at the lower end thereofto bear upon the shoulder 89 of the shaft 70. The shaft, in turn, isfirmly connected to the insert 87, either by being pressed thereinto, orby other connection means. As shown, the impellers or paddles 62 areconnected to the disc 90, through which the shaft section 91 passes,while such disc shoulders on the insert 87. Finally, the nut 92 isthreaded onto the shaft section 91 to complete the rotor assembl 99.

The housing cap 93 has the recess 94 therein into which is fitted theannular member 95 having the backing plate 96 thereon. Such member canbe of the same material as the disc element 84, and this is shown inFig. 2. The annular member 95 has a countersunk inner surface to opposethe tapered surface of the disc element, and a flat lower surface tooppose the flange face of the disc element base.

It can thus be seen that by turning the handle the shaft 70 and theelements assembled thereon and therearound may be moved axially to varythe spacing between the disc element and the annular member. Thus theorifice can be varied from the vicinity of grinding contact to somespacing, as indicated in exaggerated extent in Fig. 2, which may varyfrom almost grinding contact to A", or greater, depending upon thedesired throughput.

The fluid to be processed in the dispersator, as the mixture of oil andcaustic, enters from the line 27, via the inlet 61 into the dispersatormixing chamber 100, and passes by the impellers 62 and through theannular orifice 101 into the discharge chamber 102 from whence itpasses, via the outlet 33 into the tube 34. A coolant, as water, entersthrough the line 103, into the coolant chamber 106, from whence itcommunicates, through passages, not shown, with the jacket 105. From thecoolant chamber 106 the coolant departs, via the discharge line 104, theoil-caustic mixture being maintained at a temperature of to 150 F., arange of to 110 F. being preferred.

In case it might be desired to provide that the speed differentialbetween the disc element 84 and the annular member should be provided byalso rotating the annular member, any suitable conventional drive, notshown, could be provided to also rotate this member, and at differentspeeds from the disc element. Such differential could be provided byrotating the annular member at greater speeds, or at lesser speeds thanthe disc element, or in opposite direction from the direction ofrotation of the disc element.

In this regard it is only necessary that excessive velocities beobtained as in this way a very small volume of a more concentratedsoultion of caustic may be used, and through the excessive agitation orrate of circulation imparted thereto due to its passage with the oil andthe color bodies therein, through the restricted annular orifice, suchcaustic is assured of being thrown into intimate contact withsubstantially all of the color bodies, even though by volume such colorbodies are even less than the small amount of higher concentrate ofcaustic employed.

In summary, the excess movement imparted to the mixture of caustic andoil containing color bodies therein, in the minimum time required forpassage through the orifice, insures that, regardless of what smallpercentage the caustic may bear to the oil by volume, and regardless ofwhat even smaller percentage by volume the color bodies may bear to theoil, intimate neutralizing contact by the caustic with substantially allof the color bodies is obtained, and since the caustic is of a higherconcentration, this contact is obtained with a reduced amount ofsaponification.

Some of the other desirable efiects are: (1) Accomplishing a morethorough color removal than is possible by other processes even thoughno limitation of loss is placed upon the use of other processes. Thatis, even with higher loss experience other processes are not capable ofproducing as light an oil; (2) the process increases the efiectivenessof the reagent to an extent that has a measurable economic benefit insaving of the reagent itself; (3) the process so completely uses thereagent within the short interval of time required for dispersion thatlittle if any excess or unused caustic remains in contact with the fat.Unlike other processes where this condition prevails the loss experienceis not eflected by the time elapsing between initial contact and beforeseparation of the two phases produced by the reagent. In conventionalprocesses there remains an excess of unreacted caustic soda after mixingwhich saponifies fat when allowed to remain in contact with it therebyincreasing the loss.

This circumstance is in practice minimized as far as possible by keepingthe period of contact as short as practicable, which in most instancesis a matter of minutes. With this process, however, experience hasindicated that contact time after dispersion but before separation mayextend into days without any very significant changes in either color orloss experience; (4) it has been found by experience that this processmay be used to advantage either in conjunction with continuous or batchseparation. When this dispersion is used as a continuous process it isfollowed by treatments involving the addition of water, the raising ofthe temperature and subjected to centrifugal force wherein the soap isseparated from the fat.

With this usage it carries with it not only the principal advantage; i.e. achieving a useful color with a saving in loss, but combines thiswith a machinery simplification and an increase in capacity that ismeasured by throughput compared with conventional continuous mixers.When utilized as a batch process in conjunction with holding tankswithin which separation of phases is carried out by addition of water,elevation of temperature while stirring and subsequent separation bygravity, the process has the advantage of achieving exceptionally highproduction rates with a minimum investment in machinery and a minimumexpenditure of power.

In references to be made hereinbelow to oil colors, it is stated thatall colors referred to in this application are measured by the officialLovibond standard, A. O. C. S. method No. Cc-l3-B45.

As a specific example of this process in commercial operation, an oilstorage tank was partially filled with 125,000 pounds of cotton seed oilonce refined through the Clayton caustic soda process. This oil enteredthe tank and was maintained at a temperature of 90 F. it had a color of35 yellow and 13.1 red, and when tested by A. O. C. S. standardprocedure, exhibited a bleach color of 35 yellow-5.0 red, both colorsbeing on the Lovibond scale.

From the tank the oil was pumped by means of a centrifugal pump at arate measured by a rota-meter of 21,000 lbs/hr. to a rotating blenderoperating at a speed of approximating 880 R. P. M. In such blender itwas m xed with a measured stream of caustic soda. This caustic soda wasa 50 Baum solution pumped as a measured stream through a rota-meter at arate of 25.2 lbs./hr. at a temperature of 90 F. Thus by measuring bothoil and caustic rates, a 50 Baum solution was applied to the extent of.12%.

The oil and caustic mixture flowed from the blender to the dispersator,in a closed system, thus requiring no additional pump. and entered thedispersator at a pressure of 19 lbs. per sq. inch. This dispersator wasequipped with Carborundum disks seven inches in diameter, one stonebeing held stationary, the other revolving at 5400 R. P. M. The diskswere held so as to maintain a spacing of .017 inch.

The oil and caustic were subjected to this stone abrasion as acontinuous stream without any change in temperature, except thatresulting from the heat of the reaction which raised the mixturetemperature to approximately 94 P.

All of the oil in the original storage tank was passed as a mixture to akettle equipped with an agitating device, steam coils, and appropriateopenings. The time required for this operation approximated six hours.The oil and 150 lbs. of dispersed caustic accumulated at 94" F. at restin the kettle. Heat was applied thereto by contact with the steam coils,while the product was slowly agitated in order to avoid localover-heating, until a temperature of 140 was obtained. At this point ameasured quantity of water, amounting to 500 lbs., was sprayed over thesurface of the oil from three spray nozzles at a rate of 25 lbs. perminute. The oil was continuously agitated while the Water was beingadded, so as to expedite the contact of water with the reaction productsof the caustic and oil. At this point the water-reaction product mixturewas immiscible with the oil and showed a tendency to separate from theoil if not kept mechanically suspended by means of agitation.

The amount of water added was such as to bring about this reactionproducing condition with reference to immiscibility and specific weight,but kept low enough to avoid a cloudy oil. The agitation was thendiscontinued and the oil allowed to separate from the reacting productswhich occurs by the oil rising to the top and the reaction productscontaining the coloring matter settles to the bottom. The kettle wasallowed to stand at rest for three hours when the reaction productswhich are semi-liquid were drawn 01f. The oil remaining, and thereaction products, were weighed. The loss as oil shrinkage, as well asthe refining loss, based on the weight of the reaction products,amounted to 0.6%. The color of the treated oil was reduced to yellow-5.8red from the original 35 yellow-13.1 red, and the bleachability improvedfrom 35 ye1low-5.5 red to 18 yellow-1.7 red when measured by standard A.O. C. S. methods, and Lovibond scale.

Illustrative of the loss saving accomplished by the process is thefollowing comparison. Refined cotton seed oil having a color of 35yellow8.8 red and a bleach color of 35 yellow and 4.5 red was treatedwith caustic using the laboratory cup method, a method which Kroonenstates produces comparable losses with "High-sheer refining procedure.The same oil was treated on a conventional commercial plant scale usingconventional methods in batch equipment. Additionally, the abovedescribed machine was used and the above described steps of thisinvention employed therewith in a parallel test. In each case the amountof lye was chosen to produce substantially the same color of refined oiland oil of substantially equal bleachability. The results are tabulatedas follows:

The above tabulated results establish that the employment of the machineand process of this invention accomplished the same color as thelaboratory cup method using less than half the amount of reagent and indoing so a loss was incurred which was again less than half of thatexperienced with the laboratory method.

While the amount of caustic chosen for use in the conventional kettlemethod was slightly excessive and thereby produced a somewhat betterbleaching oil, the loss experienced was very high; so high that thesavings by the process of this invention is readily apparent.

A second comparison between the proposed method and the kettle methodcarried out in batch equipment is illustrated by the following:

Bleach Color Re- Refined Oil olor Percent Percent NaOH Loss Be. CausticConventional Kettle Method O 25 3. 77 Special Mixer (This invention) thepreceding table in that production rates were tabulated ranging between21,000 and 42,000 pounds per hour.

As a further illustration of the eliiciency of this process and theassociated low losses, the following tables are listed showing the oiltreated by the conventional laboratory method as compared with theproposed method of this invention operating under difierent rates anddifferent stone spacings. A comparison of the results clearly indicatesthat the proposed method can, as claimed above, accomplish more thoroughcolor removal, and secondly, does this with less loss. At the same timethe results illustrate the effectiveness of the type of dispersion used.As the throughput was decreased to one-fourth the starting rate and thespacing between the stones decreased to one-third the opening, there wassignificant improvement in the bleach color of the oil and noappreciable change in the loss experienced. This table illustrateswithin a partial operating range how much more elfective the colorremoval may be and how much more the effectiveness of the reagent may beincreased.

Spacing Rc-Refg. Oil Rate Between Ba. Percent Oil Bleach Percent PerHourStones, Caustic NaOH Color Color Loss inches Laboratory Cup A d 50 6 620y-21r 2.2 Special Mixing (This invention):

1 .017 105 5. 1 18y-1.7r 0. 66 .013 50 100 5.0 10y1.5r 0. 80 .009 50 1005.0 15y-1Ar 0. 84 006 50 100 5. 0 15y-1.4r 0. 84

refining process, and further shows the advantages that might beexpected from the utilization of this new process:

The following results illustrate not only the loss savings but also thecompleteness of the reaction when the dis- A Oil has original color-35yellow-8.2 red; original bleach color-35 yellow-3.4 red. "8" Oil hasoriginal color-35 yellow-8.8 red; original bleach color-35 yellow-3.4red. "C" 011 has original color-35 yellow-9.5 red; original bleachcolor35 yellow-5.0 red.

The significant points are as follows: (1) It is to be noted that thecentrifugal process has limitations with reference to the ultimatebleachability. With oils as dark as the ones utilized in this test,which are often encountered, it was not possible to produce an oilbleaching better than 1.8 red even with a relatively large amount ofcaustic utilized. This puts a severe limitation upon the centrifugal orClayton process, a limitation which is very significantly minimized byusing the process of this invention. (2) Another pertinent point isillustrated by a comparison of the production rates achieved by the twoprocesses. The centrifugal process when operating at rates between 6,000and 12,000 pounds per hour utilized between 7 and 13 centrifuges and sixmixers, while this special process operating with one mixer and thespecial dispersing machine along with one agitating tank was capable ofrates up to 42,000 pounds per hour. The last two lines of the tableimmediately hereinabove further illustrate another operating range notshown in persion is made as illustrated by the effect of allowing thecolloidal emulsion to remain unseparated for a period of eight days:

It is apparent that the reaction which takes place in the fraction of asecond elapsing during the passage of the mixture between the stone wascarried no further by allowing the mixture to stand for eight days.

The following comparison illustrates how the process 1 1 works equallywell with batch gravity separation and continuous centrifugalseparation:

Broadly this invention consists of a process of removing color fromcotton seed oil, and the like, by re-refining methods, and suchinvention broadly takes in any method and structure which is capable ofsubstantially instantaneously dispersing a caustic solution into the oilwhereby the color bodies of the oil may be so amply and intimatelycontacted by a substantially reduced quantity of the caustic refiningagent, as compared with conventional quantitative requirements, that aresultant substantially increased removal of color bodies at asubstantially reduced refining loss may be obtained.

I claim:

1. A process for removing color from previously refined vegetable oilswhich comprises dispersing a caustic solution of at least 40 Baumstrength substantially instantaneously into the oil in not more thanabout one second and in an amount that the caustic soda is in the rangeof between 0.05 and 0.14 percent by weight of the mixture of oil andcaustic solution and later separating the oil from the mixture.

2. A process for removing color bodies from previously refined vegetableoil which comprises dispersing into the oil in not more than about onesecond a caustic solution of from 40 Baum to 60 Baurn strength and in anamount that the caustic soda constitutes between 0.05 to 0.14 percent byweight of the mixture and thereafter separating the oil from themixture.

3. A process for removing color from previously refined vegetable oilwhich comprises blending said oil and a highly concentrated aqueouscaustic solution of at least 40 Baum strength and in an amount that thecaustic soda content is less than 0.14 percent by weight of the blendedmixture, forcing the blended mixture in a continuous stream of less thanone-quarter inch thick through a space between relatively movingabrasive surfaces at a rate to instantaneously disperse the caustic sodainto the oil in not more than about one second and thereafter separatingthe oil from the mixture.

4. A constant flow process of removing color bodies from previouslyrefined vegetable oil, comprising adding to the refined oil a causticsolution of at least 40 Baurn strength and in an amount that causticsoda content is by weight in the range of from about 0.055 to about 0.14percent of the mixture, passing the mixture at the rate of 5,000 to42,000 pounds per hour between opposing faces of relatively rotatablerotors operating at relative speeds of from R. P. M. to 15,000 R. P. M.with said opposing faces spaced apart from almost contact up to aboutone-quarter of an inch and thereafter separating the oil from themixture, no portion of the mixture being between said rotor surfaces formore than about one second.

5. A constant flow process of removing color bodies from previouslyrefined vegetable oil, comprising adding to the refined oil a causticsolution of at least 40 Baum strength and in an amount that the contentof caustic soda is by weight in the range of from about 0.055 to about0.14 percent of the mixture, passing the mixture in a continuouslyflowing thin stream of not more than one-quarter inch thickness betweena pair of abrasive surfaces and moving the surfaces relative to oneanother at a rate of not less than 900 R. P. M. with the rate of streamtravel such that no portion of the mixture is between the abrasivesurfaces for more than about one second and thereafter separating theoil from the mixture.

6. A process for removing color bodies from previously refined vegetableoils which comprises adding to the oil about 0.14 percent or less byweight of caustic soda in an aqueous solution of from 40 Baum to 60 Baumstrength and dispersing the caustic solution into the oil within atemperature range between approximately 60 F. and F. and in a fractionof one second by passing the mixture in a continuous stream at a rate offrom 5,000 pounds to 42,000 pounds per hour between relative movingparts spaced apart not more than one-quarter of an inch and whoserelative travel is at a rate of from about 1,649 feet per minute toabout 27,489 feet per minute and thereafter separating the oil from themixture.

References Cited in the file of this patent UNITED STATES PATENTS2,226,211 Thurman Dec. 24, 1940 2,245,112 McLean June 10, 1941 2,266,652McLean Dec. 16, 1941 2,412,251 Clayton Dec. 10, 1946 2,462,923 ThurmanMar. 1, 1949 2,644,004 Dron et a1. June 30, 1953 2,686,796 Markley etal. Aug. 17, 1954

1. A PROCESS FOR REMOVING COLOR FROM PREVIOUSLY REFINED VEGETABLE OILSWHICH COMPRISES DISPERSING A CAUSTIC SOLUTION OF AT LEAST 40* BAUMESTRENGTH SUBSTANTIALLY INSTANTANEOUSLY INTO THE OIL NOT MORE THAN ABOUTONE SECONG AND IN AN AMOUNT THAT THE CAUSTIC SODA IS IN THE RANGE OFBETWEEN 0.05 AND 0.14 PERCENT BY WEIGHT OF THE MIXTURE OF OIL ANDCAUSTIC SOLUTION AND LATER SEPARATING THE OIL FROM THE MIXTURE.
 3. APROCESS FOR REMOVING COLOR FROM PREVIOUSLY REFINED VEGETABLE OIL WHICHCOMPRISES BLENDING SAID OIL AND A HIGHLY CONCENTRATED AQUEOUS CAUSTICSOLUTION OF AT LEAST 40* BAUME STRENGTH AND IN AN AMOUNT THAT THECAUSTIC SODA CONTENT IS LESS THAN 0.14 PERCENT BY WEIGHT OF THE BLENDEDMIXTURE, FORCING THE BLENDED MIXTURE IN A CONTINUOUS STREAM OF LESS THANONE-QUARTER INCH THICK THROUGH A SPACE BETWEEN RELATIVELY MOVINGABRASIVE SURFACES AT A RATE TO INSTANTANEOUSLY DISPERSE THE CAUSTIC SODAINTO THE OIL IN NOT MORE THAN ABOUT ONE SECOND AND THEREAFTER SEPARATINGTHE OIL FROM THE MIXTURE.